Manhattan's wildly successful High Line Park -- an old elevated rail line that was retrofitted into a stunning park -- cost about $153 million. At first glance it might seem like a big investment for a park, but consider the benefits.

Not only does the city take care of a eyesore, but the popularity of High Line has brought in an estimated $2 billion in new developments, the New York Times reports.

In the five years since construction started on the High Line, 29 new projects have been built or are under way in the neighborhood, according to the New York City Department of City Planning. More than 2,500 new residential units, 1,000 hotel rooms and over 500,000 square feet of office and art gallery space have gone up.

“Cities recognize parks are good for their economies. They’re no longer a nice thing to have, but a must,” said Will Rogers, president and chief executive of the Trust for Public Land, a national conservation group in San Francisco.

The area around the park, sprinkled with small offices under 200,000 square feet, has become a draw for start-ups and creative companies.

Other cities are finding the model appealing and want to do the same with their abandoned elevated rail lines. Philadelphia is finding that it's actually more costly to tear down their abandoned elevated railway than to redevelop it like the High Line. The Reading Viaduct would cost $50 million for Philadelphia to tear down down compared to $36 million to retrofit the rail line, the Times reports.

It's a great deal when you consider the possible economic benefits that transforming old rail lines into useful public spaces could have on the local economy.

Chicago is also looking to revive a 2.65 mile elevated rail line, now called Bloomingdale Trail, that hasn't been used for its original purpose in at least 10 years. And with Rahm Emmanual now in charge, revitalization could become a reality.

After years of grass-roots work, the Bloomingdale Trail is moving forward after Rahm Emanuel, who made completing the trail one of his campaign promises, was elected mayor in February. Over the next year, design concepts and engineering work will get under way. The Bloomingdale Trail will allow bikes and dogs, interconnect with new and existing ground-level parks and cost $40 million to $75 million.

Similarly, St. Louis wants to turn a 2.1 miles of old rail trestle into a park as part of a waterfront revitalization project.

Some might question the viability of these projects in other cities that don't have the population density of New York City, but the key to success isn't to just build parks but connect them to a larger redevelopment goals of the city.

“The High Line is not easily replicable in other cities,” said James Corner, principal of James Corner Field Operations, a New York architecture firm that designed the High Line with Diller Scofidio and Renfro. “It’s not just, ‘Build a cool park and they will come.’ It’s, ‘Build a cool park and connect it to a framework.’ ”